Birds and airplanes face into the wind when taking of or landing so they can
take advantage of wind speed. If the wind were at their backs, they would not
have the control they have when facing into it. But differences exist here too:
While large birds need a prolonged takeoff run to become airborne, small birds
can jump straight into the air on takeoff; they can generally achieve lift from
zero air speed. Larger birds can fly at speeds within a minimum and maximum
range, but they cannot take flight at zero air speed. Therefore, larger birds
need to generate air speed before they can take off. The often run over the
ground or water until they reach the minimum air speed needed to take flight.

Large terrestrial birds such as eagles and hawks land on an elevated perch or a
hill whenever possible so that they can acquire flying speed by dropping off of
the perch. Seabirds achieve the same result by accelerating down the windward
slope of large waves or by paddling over the surface while flapping
energetically. Hang gliders operate on a similar principle for takeoff. Because
of a hang glider's enormous wingspan and the relative heavy weight supported by
its "wings," the flier must always head into the wind, preferably from a sloped
hill or mountain top, to attain the minimum flying speed for lift.

Tundra Swans rise laboriously from a twilight pond. To lift themselves into the
air, these large birds must propel forward over the water to gain flight
speed.

Large land birds taking off from the ground run with steps synchronized to
their wingbeats. In a motion that resembles running, most North American water
birds use their webbed feet to push themselves forward through the water for
takeoff; this motion is also synchronized with the wingbeats.